Numerous methods exist, which make it possible to check tools used for machining parts. The object of the check is to automatically establish the state of the tools used for machining a part.
The various known methods for carrying out this check are referred to hereinafter.
A first method consists of mechanically sensing the tool using sensors. This method suffers from the disadvantage of only making it possible to measure the greatest length or the largest diameter of the tool. It does not make it possible in a simple manner to carry out a multicut tool check.
A second method consists of measuring the tool holder spindle power. However, the measurement of the spindle power is only significant for machining operations in materials of considerable strength or resistance using tools with an adequate diameter requiring an infeed of power, in such a way that power variations can be measured.
A third method consists of analyzing the vibration frequencies of the tool during machining. This method requires the placing of sensors in particular positions and the comparison of the sensed frequencies with those of a healthy tool during the same machining operation. Thus, beforehand a library is formed, which contains the different characteristics of the healthy tool and this library must be controlled.
A fourth method consists of carrying out ultrasonic measurements on the tool. These measurements require the use of specific sensors and a differential liquid.
Therefore the equipment is complex and difficult to use, because the equipment used for carrying out the checks must be withdrawable so as not to disturb the machining operations of the parts during the different machining cycles.
A fifth and final known method consists of carrying out a comparison of the machining of the tool with a predetermined model. For this purpose the system has a camera making it possible to take a picture of the tool after machining a part and processing means making it possible to compare the image obtained with a model stored in the memory. This method makes it necessary to form models of all the tools in the magazine and to produce a library containing all these models.
For elongated tools (drills, taps), a tool picture library takes up roughly one kbyte per tool and two kbyte per tool in the case of compact tools (milling cutters).
In general terms and in all the aforementioned methods, checking takes place by the comparison of certain characteristics of the tool following machining operations, relative to the same characteristics which have been predetermined for all the tools of the magazine and which are stored in a memory so as to constitute a library.
Apart from the disadvantages referred to hereinbefore and which apply to each of these methods, they also suffer from the disadvantage of making it necessary to produce a library, which is sometimes difficult to control and takes up a large amount of memory space.